SANTA CLARA – Running back LaMichael James sustained a dislocated elbow during 49ers practice on Sunday and could miss about a month of action, a source told CSNBayArea.com.

James was injured during a routine blitz pickup drill. He immediately dropped to the ground after his collision with linebacker Michael Wilhoite and was in extreme pain. He was carted off the field to the 49ers locker room.

In October, 2011, James sustained a dislocated right elbow against Cal. He returned to action 23 days later. On Sunday, James initially appeared to injure his left elbow. However, there were later indications it was his right elbow.

James entered training camp competing for a role in the 49ers’ offense. He is the team’s top return man. James averaged 10.9 yards on 23 punt returns last season.

The 49ers open the regular season in six weeks, on Sept. 7, at the Dallas Cowboys.

“As I watched him through the offseason you could see it getting better every single day,” 49ers coach Jim Harbaugh said of Lattimore. “To ballpark a percentage, that would be hard to do. But it’s not yet 100 and I say that more from a physical aspect than from a mental. When it gets to that point then he has the best chance to compete out there.”